U.S. patent application number 11/659429 was filed with the patent office on 2008-05-08 for method and device for processing carbon bodies.
Invention is credited to Jens Bugge Hatlevoll, Oddvin Nesse, Jan Egil Pallin, Hans Seehuus.
Application Number | 20080107489 11/659429 |
Document ID | / |
Family ID | 35044472 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080107489 |
Kind Code |
A1 |
Nesse; Oddvin ; et
al. |
May 8, 2008 |
Method And Device For Processing Carbon Bodies
Abstract
The present invention concerns a method and a device for
processing calcinated carbon bodies such as anodes or cathodes for
use in connection with electrolytic production of aluminium. The
carbon bodies are processed using a rotating processing tool (1)
that consists of a mainly circular disc with cutting edges (12,
12') mounted at its periphery. The cutting edges may be made of
polycrystalline diamond (POD) or an equivalent material. With the
present invention it is possible to create slots in calcinated
carbon bodies in an efficient manner with low tool wear.
Inventors: |
Nesse; Oddvin;
(Ardalstangen, NO) ; Pallin; Jan Egil; (Heimdal,
NO) ; Seehuus; Hans; (Melhus, NO) ; Hatlevoll;
Jens Bugge; (Ardalstangen, NO) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W., SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
35044472 |
Appl. No.: |
11/659429 |
Filed: |
July 15, 2005 |
PCT Filed: |
July 15, 2005 |
PCT NO: |
PCT/NO05/00261 |
371 Date: |
August 14, 2007 |
Current U.S.
Class: |
407/51 ;
83/13 |
Current CPC
Class: |
Y10T 407/1942 20150115;
B28D 1/121 20130101; Y10T 82/10 20150115; Y10T 83/04 20150401; Y10T
407/22 20150115; B23D 61/04 20130101; Y10T 82/125 20150115 |
Class at
Publication: |
407/51 ;
83/13 |
International
Class: |
B26D 1/157 20060101
B26D001/157; B26D 1/00 20060101 B26D001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2004 |
NO |
20043412 |
Claims
1-13. (canceled)
14. A method for processing calcinated carbon bodies such as anodes
or cathodes for use in connection with electrolytic production of
aluminium, in which the carbon bodies are processed by means of a
rotating processing tool (1), wherein the processing tool (1) has
cutting edges (12) at its outer periphery that are made out of a
material with durability and suitability for processing calcinated
carbon material, where said processing tool is used for making
slot(-s) in said carbon bodies.
15. A method in accordance with claim 14, wherein cutting edges are
moved at a speed greater than 100 m/min. and less than 300 m/min.
relative to the carbon body.
16. A method in accordance with claim 15, wherein the speed is in
the order of 200 m/min.
17. A method in accordance with claim 14, wherein the processing
tool is designed to move along a linear path.
18. A method in accordance with claim 14, wherein the carbon body
is moved along a linear path relative to the processing tool.
19. A method in accordance with claim 14, wherein the cutting edges
(12) have a cutting surface that processes the carbon body at an
angle in the order of 5-15.degree. to the radius of the processing
tool.
20. A device for processing calcinated carbon bodies such as anodes
or cathodes for use in connection with the electrolytic production
of aluminium, whereby the carbon bodies are processed by means of a
rotating processing tool (1), wherein the processing tool consists
of a mainly circular disc with cutting edges (12, 12') mounted at
its periphery, where said cutting edges are made out of a material
with durability and suitability for processing calcinated carbon
material and further arranged for processing slot(-s) in said
carbon bodies.
21. A device in accordance with claim 20, wherein the cutting edges
of the processing tool (12, 12') are mounted in cutting edge
holders (7, 7').
22. A device in accordance with claim 21, wherein the cutting edge
holders (7, 7') are mounted alternately on each-side of the
disc.
23. A device in accordance with claim 20, wherein the cutting edges
(12, 12') are made of polycrystalline diamond (PCD).
24. A device in accordance with claim 20, wherein the cutting
surface of the cutting edges is at an angle in the order of
5-15.degree. to the radius of the processing tool.
25. A device in accordance with claim 20, wherein the cutting
surface of the cutting edges is at an angle in the order of
10.degree. to the radius of the processing tool.
26. A device in accordance with claim 20, wherein two or more
processing tools are mounted axially displaced on the same shaft
for simultaneous creation of two or more slots.
Description
[0001] The present invention relates to a method and a device for
processing carbon bodies. In particular, the present invention
concerns the processing of grooves or slots in calcinated carbon
bodies.
[0002] In aluminium electrolysis using the so-called Hall-Heroult
method with prebaked anodes, gas bubbles are created at the wearing
(or consumable) surfaces of the anodes (mainly underneath
them).
[0003] The presence of a gas layer means that the electrical
resistance towards the bath increases, resulting in reduced current
efficiency. In accordance with the prior art, solutions are
proposed that involve ducts or grooves being created in the wearing
surfaces of the anodes in order to drain the gas away, conduct it
out of the bath and collect it in a degassing system. The prior art
also proposes creating longitudinal grooves in the cathode carbon
in order to be able to incorporate electrically conductive cathode
rods.
[0004] Grooves in carbon bodies can be formed or preformed when the
bodies are in a green state, i.e. before calcination or baking. One
disadvantage of this is that the geometry of the grooves may be
changed during handling and baking on account of creep or external
mechanical stress. Such preforming may result in density gradients
in the anode and rejects in the process. It may therefore be
necessary to process (calibrate) the grooves so that they have the
correct geometry.
[0005] The prior art also proposes processing holes in calcinated
carbon bodies using mechanical equipment comprising a milling head
that is similar to a drill bit for drilling bedrock, see EP
0922516. However, this equipment is not appropriate for creating
slots with an extent equivalent to that of the carbon body, as it
generally rotates around an axis perpendicular to the surface of
the body and will suffer from capacity restrictions in connection
with such a task.
[0006] US 2003/0075163 A1 describes a saw blade with inserts partly
of polycrystalline diamond and partly of a carbide material. The
blade is suitable for sawing a composite material comprising
cement, ground sand and cellulose fibre, which is a material with
completely different properties and which therefore also requires a
different processing process than the present material.
[0007] The present invention represents a method and a device that
allow effective, precise processing of slots in calcinated carbon
bodies, while the life of the equipment is considerably greater
than what can be achieved using available technology. One problem
with the processing of calcinated carbon electrodes is that the use
of liquid for cooling/lubricating the tool during processing must
be avoided, as moisture in the electrodes may result in major
disadvantages for electrolysis. Moreover, calcinated carbon
material is relatively porous so that, if liquid is used, the
electrodes must undergo a comprehensive cleaning/drying process.
These disadvantages mean that it is desirable to carry out the
processing without the presence of cutting/cooling liquid, which
increases the load on the processing tool. In theory, it would be
conceivable to process the carbon bodies immediately after they
have been calcinated in a furnace so that the residual heat is used
to dry any liquid applied to the bodies. However, such a processing
process might also produce increased thermal load on the tool and
the carbon bodies. The limitations of the prior art equipment are
primarily in the processing tool itself. A tool has thus been
developed that is shaped as a circular disc with cutting edges
along the periphery (like a saw blade) to solve the present
problems. One advantage is that the geometry and material of the
cutting edges contribute to a considerable increase in life in
relation to what has been possible with prior art technology. With
the present solution, slots can be created In calcinated carbon
bodies even without them being preformed in a green state.
[0008] The above and other advantages can be achieved with the
invention as it is defined in the attached claims.
[0009] The present invention will be described in further detail in
the following using figures and examples, where:
[0010] FIG. 1 shows a processing tool in accordance with the
present invention, seen from the side,
[0011] FIG. 2 shows an enlarged section of the processing tool
shown in FIG. 1,
[0012] FIG. 3 shows a section of the processing tool in accordance
with the present invention, seen from the front,
[0013] FIG. 4 shows a perspective view of a section of the
processing tool shown in FIG. 1.
[0014] FIG. 1 shows a processing tool 1 in the form of a circular
disc with a boss 2 for mounting on a spindle in a machining unit or
processing machine. The mounting holes 3 allow the processing tool
to interact with bolts or projections on a flange on the spindle
(not shown). The processing machine may be of a prior art type that
allows the processing tool to rotate and to move linearly along a
path corresponding to the extent and depth of the slot to be
created. The machine may have additional equipment for handling and
fixing the body to be processed (not shown). Such machines are
available in a wide range of embodiments with which one skilled
person is familiar and will not, therefore, be described in further
detail here. As an alternative, the spindle may be stationary,
while the body to be processed is moved in relation to it.
[0015] The processing tool 1 also has a central annular part 4,
which extends from the boss to an outer peripheral part 5. Both the
central annular part 4 and the outer peripheral part 5 may comprise
slits or holes for better stability, among other things in relation
to thermal stress. In particular, the outer peripheral part 5 is
provided with slits 6 that ensure that thermal expansion in this
area does not affect the flatness of the processing tool. Moreover,
the slits will ensure a certain degree of springing or dampening of
impacts that may occur in a tangential direction to the blade
during the processing process. As the Figure also shows, the
processing tool is enmeshed with a base 8.
[0016] In FIG. 1, an area by the periphery of the processing tool
is marked with a ring 9. Within the ring are 3 cutting edge holders
7 with cutting edges, which will be described in further detail
with reference to FIG. 2.
[0017] FIG. 2 shows a section of the processing tool shown in FIG.
1. In the outer peripheral part 5 are cutting edge holders 7, only
one of which will be explained in further detail. In this
connection, please also see FIG. 4, which shows a cutting edge
holder in perspective. The cutting edge holder 7 may consist of a
polygon. In this example, a pentagon is shown. The cutting edge
holder may be fixed to the outer peripheral part 5 by means of one
or more fixings 11 through holes 14. Such fixings may consist of
screws, rivets, etc. Alternatively, these parts may be joined by
means of other available fixing techniques such as welding, gluing,
etc.
[0018] The cutting edge holder 7 may also comprise a cutting edge
12 that may preferably be made of polycrystalline diamond (PCD).
Other ceramics, composites or alloys with corresponding durability
and suitability for processing calcinated carbon material may also
be used.
[0019] The cutting edge 12 may be mounted in the cutting edge
holder by means of various techniques based on gluing, braze
welding, soldering, mechanical attachment, etc. As shown in the
Figure, the cutting edge in this example is mounted so that its
cutting surface is at a 10.degree. angle to the radius of the
processing tool or a perpendicular to the periphery at this point.
Other angles may also be used. It is expedient for the angle to be
in the order of 5-15.degree..
[0020] FIG. 3 shows a section of the processing tool 1, seen from
the front. As the figure shows, the cutting edge holders 7, 7' may
be mounted alternately against each side of the processing tool.
The primary result of this is that the cutting edges 12, 12' may be
mounted with a lateral displacement, which means that the slot that
is processed may be made wider than if the cutting edges were
mounted in a row. Moreover, the alternate displacement of the
cutting edges means that both the cutting of material and transport
of chips are very efficient in relation to the material to be
processed.
[0021] Tests and experiments carried out show that good cutting of
chips and low wear on the tool can be achieved when the speed of
the cutting edges relative to the carbon body to be processed is in
the range 100-300 metres per minute (m/min.). The particularly
preferred speed is in the order of 200 m/min.
[0022] The speed of the cutting edges will partly depend on the
composition and degree of calcination of the carbon body being cut.
The size of particles and the content of anthracite, coke, pitch,
binder, etc. in the formula may also be significant to the
determination of the optimal cutting speed, Moreover, the static
forces acting on the processing tool relative to the carbon body,
plus the size and form of the cut chips, will also influence how
the optimal cutting speed is to be determined.
[0023] Long-term tests show that it can be possible to mill slots
in 20,000 anodes with the present processing tool before the tool
needs to be replaced/overhauled. Tests carried out with available
equipment resulted in considerable wear after just 200-300 anodes,
and the tool had to be replaced/overhauled.
[0024] Slots created in anodes may be in the vertical plane and
have a width of approximately 1 cm or more. Moreover, they may be
so deep that the slots are present throughout the life of the
anode. With current anode heights, this means that the slots are
processed to a depth of approximately 35 cm. Moreover, they may be
inclined so that gas can be drained towards one side of the anode.
The inclination may be approximately 3 cm from one end of the slot
to the other and may be produced by the anode being moved relative
to the processing tool during processing.
[0025] Slots of a certain extent, for example 15 cm deep, may be
preformed in a green state, after which the processing tool is used
to remove any residue of packing coke from the calcination and to
process the rest of the slot. This may reduce wear on the tool and
the quantity of carbon material that is removed and needs to be
handled (returned to the anode production process).
[0026] Moreover, several parallel slots may be arranged
simultaneously in the carbon body by two or more processing tools
being used on the body simultaneously, for example by their being
arranged on the same rotating shaft at a certain axial distance
from each other.
[0027] The machining unit may be enclosed to protect the
environment against noise and dust, and it may comprise an
extraction system.
[0028] Forms of processing of carbon bodies other than the creation
of slots may also be carried out with the present invention. For
example, the tool may be used for the calibration of or removal of
burrs from the outer geometry of carbon bodies. In such case, the
tool may be arranged so that it can be moved in all three axial
directions, i.e. along a linear path, downwards and sideways.
[0029] Moreover, it may be relevant to create dovetail-shaped or
undercut slots with the processing tool. The tool must then be
permitted to rotate and move around an axis that is inclined or
skew-oriented to the carbon body to be processed.
* * * * *